FREE - Open source project - Stable version available - http://www.js-examples.com/forum/ to see it in action.
This forum provides almost every imaginable thing you could want in a forum system. It runs on perl cgi scripts which use a mysql database. Easy to configure the session module as well as the forum module - a email receving/sending module is also available.

A simple structure and easy to install BBS script. You can turn the HTML tags on or off by setting the variables inside the script. The script also supports footer and header, so you can make every post look like rest of your pages.